I stared at the horse who had just sprung from the wheelchair: a huge white stallion. But where its neck should be was the upper body of my Latin teacher, smoothly grafted to the horse's trunk.

"What a relief," the centaur said. "I'd been cooped up in there so long, my fetlocks had fallen asleep. Now, come, Percy Jackson. Let's meet the other campers."

Once I got over the fact that my Latin teacher was a horse, we had a nice tour, though I was careful not to walk behind him. I'd done pooper-scooper patrol in the Macy's Thanksgiving Day Parade a few times, and, I'm sorry, I did not trust Chiron's back end the way I trusted his front.

We passed the volleyball pit. Several of the campers nudged each other. One pointed to the minotaur horn I was carrying. Another said, "That's him."

Most of the campers were older than me. Their satyr friends were bigger than Grover, all of them trotting around in orange CAMP HALF-BLOOD T-shirts, with nothing else to cover their bare shaggy hindquarters. I wasn't normally shy, but the way they stared at me made me uncomfortable. I felt like they were expecting me to do a flip or something.

I looked back at the farmhouse. It was a lot bigger than I'd realized—four stories tall, sky blue with white trim, like an upscale seaside resort. I was checking out the brass eagle weather vane on top when something caught my eye, a shadow in the uppermost window of the attic gable. Something had moved the curtain, just for a second, and I got the distinct impression I was being watched.

"What's up there?" I asked Chiron.

He looked where I was pointing, and his smile faded. "Just the attic."

"Somebody lives there?"

"No," he said with finality. "Not a single living thing."

I got the feeling he was being truthful. But I was also sure something had moved that curtain.

"Come along, Percy," Chiron said, his lighthearted tone now a little forced. "Lots to see."

We walked through the strawberry fields, where campers were picking bushels of berries while a satyr played a tune on a reed pipe.

Chiron told me the camp grew a nice crop for export to New York restaurants and Mount Olympus. "It pays our expenses," he explained. "And the strawberries take almost no effort."

He said Mr. D had this effect on fruit-bearing plants: they just went crazy when he was around. It worked best with wine grapes, but Mr. D was restricted from growing those, so they grew strawberries instead.

I watched the satyr playing his pipe. His music was causing lines of bugs to leave the strawberry patch in every direction, like refugees fleeing a fire. I wondered if Grover could work that kind of magic with music. I wondered if he was still inside the farmhouse, getting chewed out by Mr. D.

"Grover won't get in too much trouble, will he?" I asked Chiron. "I mean… he was a good protector. Really."

Chiron sighed. He shed his tweed jacket and draped it over his horses back like a saddle. "Grover has big dreams, Percy. Perhaps bigger than are reasonable. To reach his goal, he must first demonstrate great courage by succeeding as a keeper, finding a new camper and bringing him safely to Half-Blood Hill."

"But he did that!"

"I might agree with you," Chiron said. "But it is not my place to judge. Dionysus and the Council of Cloven Elders must decide. I'm afraid they might not see this assignment as a success. After all, Grover lost you in New York. Then there's the unfortunate… ah… fate of your mother. And the fact that Grover was unconscious when you dragged him over the property line. The council might question whether this shows any courage on Grover's part."

I wanted to protest. None of what happened was Grover's fault. I also felt really, really guilty. If I hadn't given Grover the slip at the bus station, he might not have gotten in trouble.

"He'll get a second chance, won't he?"

Chiron winced. "I'm afraid that was Grover's second chance, Percy. The council was not anxious to give him another, either, after what happened the first time, five years ago. Olympus knows, I advised him to wait longer before trying again. He's still so small for his age…"

"How old is he?"

"Oh, twenty-eight."

"What! And he's in sixth grade?"

"Satyrs mature half as fast as humans, Percy. Grover has been the equivalent of a middle school student for the past six years."

"That's horrible."

"Quite," Chiron agreed. "At any rate, Grover is a late bloomer, even by satyr standards, and not yet very accomplished at woodland magic. Alas, he was anxious to pursue his dream. Perhaps now he will find some other career…"

"That's not fair," I said. "What happened the first time? Was it really so bad?"

Chiron looked away quickly. "Let's move along, shall we?"

But I wasn't quite ready to let the subject drop. Something had occurred to me when Chiron talked about my mother's fate, as if he were intentionally avoiding the word death. The beginnings of an idea—a tiny, hopeful fire—started forming in my mind.

"Chiron," I said. "If the gods and Olympus and all that are real…"

"Yes, child?"

"Does that mean the Underworld is real, too?"

Chiron's expression darkened.

"Yes, child." He paused, as if choosing his words carefully. "There is a place where spirits go after death. But for now… until we know more… I would urge you to put that out of your mind."

"What do you mean, 'until we know more'?"

"Come, Percy. Let's see the woods."

As we got closer, I realized how huge the forest was. It took up at least a quarter of the valley, with trees so tall and thick, you could imagine nobody had been in there since the Native Americans.

Chiron said, "The woods are stocked, if you care to try your luck, but go armed."

"Stocked with what?" I asked. "Armed with what?"

"You'll see. Capture the flag is Friday night. Do you have your own sword and shield?"

"My own—?"

"No," Chiron said. "I don't suppose you do. I think a size five will do. I'll visit the armory later."

I wanted to ask what kind of summer camp had an armory, but there was too much else to think about, so the tour continued. We saw the archery range, the canoeing lake, the stables (which Chiron didn't seem to like very much), the javelin range, the sing-along amphitheater, and the arena where Chiron said they held sword and spear fights.

"Sword and spear fights?" I asked.

"Cabin challenges and all that," he explained. "Not lethal. Usually. Oh, yes, and there's the mess hall."

Chiron pointed to an outdoor pavilion framed in white Grecian columns on a hill overlooking the sea. There were a dozen stone picnic tables. No roof. No walls.

"What do you do when it rains?" I asked.

Chiron looked at me as if I'd gone a little weird. "We still have to eat, don't we?" I decided to drop the subject.

Finally, he showed me the cabins. There were twelve of them, nestled in the woods by the lake. They were arranged in a U, with two at the base and five in a row on either side. And they were without doubt the most bizarre collection of buildings I'd ever seen.

Except for the fact that each had a large brass number above the door (odds on the left side, evens on the right), they looked absolutely nothing alike. Number nine had smokestacks, like a tiny factory. Number four had tomato vines on the walls and a roof made out of real grass. Seven seemed to be made of solid gold, which gleamed so much in the sunlight it was almost impossible to look at. They all faced a commons area about the size of a soccer field, dotted with Greek statues, fountains, flower beds, and a couple of basketball hoops (which were more my speed).

In the center of the field was a huge stone-lined firepit. Even though it was a warm afternoon, the hearth smoldered. A girl about nine years old was tending the flames, poking the coals with a stick.